RFC 5211

An Internet Transition Plan

Network Working Group J. Curran
Request for Comments: 5211 July 2008
Category: Informational
An Internet Transition Plan
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
IESG Note
This RFC is not a candidate for any level of Internet Standard. The
IETF disclaims any knowledge of the fitness of this RFC for any
purpose and notes that the decision to publish is not based on IETF
review apart from IESG review for conflict with IETF work. RFC
Editor has chosen to publish this document at its discretion. See
RFC 3932 for more information.
Abstract
This memo provides one possible plan for transitioning the Internet
from a predominantly IPv4-based connectivity model to a predominantly
IPv6-based connectivity model.
Table of Contents
1. Introduction ....................................................21.1. Requirements Language ......................................22. A Phased Transition Model .......................................22.1. Preparation Phase - Present to December 2009 ...............32.2. Transition Phase - January 2010 to December 2011 ...........42.3. Post-Transition Phase - January 2012 to the Future .........43. Summary .........................................................54. Security Considerations .........................................55. IANA Considerations .............................................56. Acknowledgments .................................................67. References ......................................................67.1. Normative References .......................................67.2. Informative References .....................................6

1. Introduction
This memo provides one possible plan for transitioning the Internet
from a predominantly IPv4-based connectivity model to a predominantly
IPv6-based connectivity model.
Other transition plans are possible and this purely informational
document does not create an obligation on any party to undertake any
of the actions specified herein, and the use of requirements language
per RFC 2119 is only for the purpose of clearly describing the
proposed transition plan in unambiguous terms.
The motivation for an Internet-wide transition plan is to facilitate
coordination of expectations among innumerable, highly decentralized
entities during a period of significant change, thus reducing risk to
the defining Internet property of universal connectivity.
The purpose of specifying this particular transition plan is to allow
for overall assessment of the challenges of accomplishing the desired
transition and to continue the discussion of Internet-wide transition
plans in general.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
RFC 2119 defines the use of these key words to help make the intent
of Standards Track documents as clear as possible. While not a
Standards Track document, the same key words are used in this
document only for sake of clarity in describing the proposed
transition plan.
2. A Phased Transition Model
It is not reasonable to specify the changes that each and every
system connected to the Internet must undergo in order to achieve the
desired transition, as the number of connected systems precludes
creating one plan that contains such a level of detail. Further,
while there are common scenarios that may be specified for
transitioning individual networks (refer to [RFC3750] and [RFC4057]
for examples), the specific timeline and mechanisms utilized for a
given network will be unique. Despite these challenges, it is
necessary to coordinate expectations on an overall basis so that
Internet-wide connectivity is maintained throughout the transition.

This document specifies a three-phase transition plan that includes
preparation, transition, and post-transition phases, and delineates
the necessary activities within each phase based on the role that an
organization plays in the provision and use of Internet services.
An important distinction made in this transition plan is identifying
the explicit requirement for existing end-site organizations to add
IPv6-based connectivity to their public-facing servers during a
transition phase. An accelerated adoption of IPv6 for public-facing
servers enables new organizations in the post-transition phase to be
connected to the Internet only via IPv6 and still have access to a
substantial representative base of publicly available servers.
For nearly every organization, the task of IPv6-enabling their
public-facing servers is far easier than undertaking an
organization-wide adoption of IPv6. Still, the requirement for
existing Internet-connected organizations to add IPv6 connectivity
(even to a small number of systems) will be a significant hurdle and
require a level of effort that may not be achievable given the lack
of compelling additional benefits to these organizations [RFC1669].
This transition plan presumes that "connectivity is its own reward"
[RFC1958] and that there still exists a sufficient level of
cooperation among Internet participants to make this evolution
possible.
The three proposed phases are: Preparation Phase, Transition Phase,
and Post-Transition Phase. The timeline for the phases has been set
to allow entry to the Post-Transition Phase prior to the projected
IPv4 address pool exhaustion date [IPUSAGE].
2.1. Preparation Phase - Present to December 2009
In the Preparation Phase, Service Providers pilot test their IPv6
network services, and end-site organizations prepare to provide
Internet-facing services via IPv6-based connectivity while continuing
to provide Internet-facing services via IPv4 connectivity.
During the Preparation Phase, the following principles apply:
PREP1: Service Providers SHOULD offer pilot IPv6-based Internet
Service to their Internet customers. IPv6-based Internet
Service MAY be provided via IPv6 transition mechanisms (such
as those described in [RFC4213], for example) or via native
IPv6 network service.

PREP2: Organizations SHOULD arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6 servers
in this phase SHOULD use separate service names per [RFC4472]
to avoid impact to production IPv4-based services unless the
organization supports production IPv6 connectivity.
PREP3: Organizations MAY provide IPv6-based Internet connectivity to
internal user communities.
2.2. Transition Phase - January 2010 to December 2011
In the Transition Phase, Service Providers offer production IPv6 and
IPv4 services to their Internet customers. End-site organizations
provide Internet-facing services in a production manner via IPv6-
based connectivity in addition to IPv4-based connectivity.
During the Transition Phase, the following principles apply:
TRANS1: Service Providers MUST offer IPv6-based Internet Service to
their Internet customers. IPv6-based Internet Service SHOULD
be via native IPv6 network service but MAY be via IPv6
transition mechanisms if necessary.
TRANS2: Organizations MUST arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6
servers SHOULD be treated as production by the organization,
and SHOULD be treated as production by other Internet
organizations.
TRANS3: Organizations SHOULD provide IPv6-based Internet connectivity
to their internal user communities, and provide IPv6 internal
supporting servers (e.g., DNS, DHCP). IPv6-based Internet
connectivity MAY be via native IPv6 network service or MAY be
via IPv6 transition mechanisms.
2.3. Post-Transition Phase - January 2012 to the Future
In the Post-Transition Phase, end-site organizations provide all
Internet-facing services via IPv6-based connectivity, thus allowing
for new Internet customers connected solely by IPv6.
During the Post-Transition Phase, the following principles apply:
POST1: Service Providers MUST offer IPv6-based Internet Service to
their Internet customers. IPv6-based Internet Service SHOULD
be via native IPv6 network service.

POST2: Organizations MUST arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6 servers
MUST be treated as production by the organization, and SHOULD
be treated as production by other Internet organizations.
POST3: Organizations SHOULD provide IPv6-based Internet connectivity
to internal user communities, and provide IPv6 internal
supporting infrastructure (e.g., routers, DNS, DHCP, etc).
IPv6-based Internet connectivity SHOULD be via native IPv6
network service or MAY be via IPv6 transition mechanisms.
POST4: Service Providers MAY continue to offer IPv4-based Internet
connectivity to their Internet customers. Organizations MAY
continue to use IPv4-based Internet connectivity.
3. Summary
In order to facilitate full Internet-wide connectivity during the
transition from IPv4-based connectivity to IPv6-based connectivity, a
transition plan which provides clear guidance to organizations
regarding expectations is necessary. As the specific expectations
change over time, and vary greatly by organization, a phased approach
is specified in this document, with the timeline for each phase set
with the intention of allowing enough time for the necessary planning
and deployment steps which each organization much undertake. This
Internet Transition Plan provides for transition to predominantly
IPv6-connectivity by January 2012 which, with careful management, may
meet the overall requirements of allowing the Internet to scale as
specified in "The Recommendation for the IP Next Generation Protocol"
[RFC1752].
4. Security Considerations
This memo describes the transition of the Internet from IPv4-based
connectivity to predominantly IPv6-based connectivity. This change
inherently has security implications due to the widespread deployment
of a new version of the Internet Protocol but these are beyond the
scope of this document and are covered in [RFC4942]. This document
raises no new security issues itself.
5. IANA Considerations
While no new name or identifier space is created by this document,
the policies for management of Internet Protocol version 4 (IPv4)
address space may not provide for IPv4 availability through the
Transition Phase as intended by this plan. The IANA should work with

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